THE RECONSTRUCTIONS OF THE PB(110) SURFACE STUDIED BY LOW-ENERGY-ELECTRON MICROSCOPY

Several reconstructions of the Pb(110) surface and their transformatio ns have been investigated with low energy electron microscopy and diff raction. Although the c(2 X 4) order-disorder transition of the clean surface was seen clearly to be first order, variation of the transitio n temperature, T-tl approximate to 420 K, by at least 25 K across the surface indicates the presence of significant heterogeneity. Locally v arying stress of sufficient magnitude to effect the c(2 X 4) phase tra nsition broadening may be ultimately responsible for driving this reco nstruction and its evolution into a (2 X n) form. Potassium-induced c( 5 X 2) and c(2 X 4) structures, which we attribute to substrate recons truction, have also been discovered here. These impurity-induced struc tures are distinguished from the clean surface reconstruction by their periodicities and/or disordering temperatures. The occurrence of both clean surface and alkali-activated c(2 X 4) reconstructions suggests that a common origin is shared with the widely studied clean and alkal i-induced (1 X 2) reconstructions of the other fee metal (110) surface s.